Abstract: The present invention provides a device and method of non-destructively monitoring reactive material through a substrate for changes in material properties that designate the condition of the reactive material during cure and service life. A transducer is placed on a portion of the substrate generally parallel to an interface of the substrate to the reactive material. The ultrasonic waves generated via the transducer are used to detect reflected sound waves upon encountering the interfaces, where the interfaces consist of changes in material properties across the substrate.

Abstract: A method of connecting hollow conductors with a brazing alloy employs a measuring mechanism 10 for measuring a connecting state of a connecting portion after brazing hollow conductors. The measuring mechanism comprises a scanner 101 and a holder 19, which are separated in advance, so that the mechanism can be installed in a narrow space. A display mechanism 20 displays measuring results as tow-dimensional patterns, and the evaluation mechanism 30 evaluate the connecting portions by an area of the defects and an integral length of sound portions. A judgment mechanism 40 evaluates relative relation of the measuring results with causes-and-defects, which are previously stored, and shows the cause of the defect.

Abstract: A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat is disclosed. A monolithic piezoelectric transducer (MPT) productive of a test signal having a defined angle of refraction with respect to the tooth material is selected. The MPT is positioned at an outer surface of the tooth and oriented so as to direct the test signal to propagate through the tooth toward a load surface of the tooth where a butt joint of a set of wedges is disposed. The MPT is activated so as to test the load surface proximate the butt joint for cracks thereat.

Abstract: A method for ultrasonically inspecting a generator field tooth for the detection, characterization and/or sizing of cracks thereat is disclosed. An electromagnetic acoustic transducer (EMAT) productive of a test signal having a defined angle of refraction with respect to the tooth material is selected. The EMAT is positioned at an outer surface of the tooth absent a fluid couplant and oriented so as to direct the test signal to propagate through the tooth toward a load surface of the tooth where a butt joint of a set of wedges is disposed. The EMAT is activated so as to test the load surface proximate the butt joint for cracks thereat.

Abstract: The invention relates to a method for determining the size of a fracture (26) in a workpiece (20), in particular the depth of a fracture (26) in said workpiece (20), by means of the ultrasound pulse method, comprising the following method steps: a workpiece (20), with a front surface (22) and a back surface (24), having a fracture (26), extending from the back surface (24) and an angle test head (28) is applied to the front face (22), transmits ultrasound pulses at an angle alpha into the workpiece (20) and receives echoes from said pulse, the angle test head (28) is moved at least once over the fracture (26), such that the radiation beam (46) from the angle test head (28) completely covers the fracture (26), the received echo signals are digitized and stored in a memory (40) as variable pairs of echo signal versus runtime, the variable pairs form a value upwardly defined by an envelope (48) and the dimension of the fracture (26) is determined from the width of the envelope (48) at a given partial amplitude a

Abstract: A system for inspecting a refractory furnace having an outer shell and an inner refractory brick lining includes a stress wave generator for generating stress waves that propagate through the outer shell and the refractory brick lining. A stress wave sensor senses reflected stress waves returning to the outer shell. A processing unit in communication with the stress wave sensor processes output generated by the stress wave sensor to generate data representing the condition of the refractory brick lining. In this manner, the location and geometry of anomalies within the refractory brick lining can be determined without requiring the refractory furnace to be shut down.

Abstract: A system to perform measurements on liquids, meat, viscous sugar or starch-based materials, and other foodstuffs using air-coupled ultrasound is provided. The technique uses ultrasonic transducers (advantageously capacitive transducers with polymer membranes), to generate ultrasonic signals in air, and to receive these signals after they have passed through the material under test. An ultrasonic pulse-compression process is then applied to increase the sensitivity of signals transmitted through the materials.

Abstract: A method and apparatus for detecting and automatically identifying defects in technical equipment, is disclosed. Measurement signals varying in time are downloaded as spectrograms to a computer memory. Using a predetermined criteria a set of designated peak values is created. Using another predetermined criteria the set of designated peak values is divided into two subsets. Then in one of the subsets, peak groups differing from each other by the basic frequency values are distinguished. The second subset, created from the set of designated peak values, is searched for the presence of sidebands for peaks from each specified peak group and if the sidebands are present the basic frequency of the sidebands is calculated. Then the existence of a defect in the technical equipment is detected, and identified by comparing the basic frequencies and the basic frequencies of the sidebands with the frequency values collected in the computer memory.

Abstract: A method and system for ultrasonically inspecting turbine wheels and other disk-shaped articles having a central opening and multiple secondary openings radially spaced outward from the central opening. At least one ultrasonic transducer is placed in at least one of the secondary openings of the wheel. The transducer is configured and oriented to perform a pulse-echo diagnostic technique on the wheel by emitting ultrasonic signals that intersect radials of the wheel at angles of approximately ninety degrees to the radials. The ultrasonic signals intersect the radials at points so that a plurality of points are located on a plurality of radials. The points define a locus of points through the volume of the wheel between the central opening and the secondary opening, such that the volume is inspected for defects. The transducer receives ultrasonic signals that are reflected from one or more points when a defect is encountered.

Abstract: A method for determining incipient mechanical failure of an object includes insonifying the object with ultrasonic energy at a selected fundamental frequency. Amplitude data is acquired from the insonified object at the fundamental frequency and at a second harmonic of the fundamental frequency, and a non-linear acoustic image is generated from the amplitude data at the fundamental frequency and the second harmonic frequency.

Abstract: A method of measuring the adhesion of a coating to a substrate, wherein the measurement is done in air and wherein an ultrasound transducer is applied to the substrate by means of a thin film of gel, and a quality factor is calculated, given by the ratio between the amplitudes of the echoes associated with the first two reflections on the substrate/coating interface after passing through the substrate or on the coating/air interface after passing through the substrate and the coating.

Abstract: A system for inspecting adhesive in a composite structure, such as for soft or improperly cured regions, includes a transducer and a processing element. The transducer can transmit a signal, such as an ultrasonic signal, into the adhesive such that at least a portion of the ultrasonic signal can propagate through the adhesive, reflect off of an interface between the adhesive and another material, and propagate back through the adhesive. Upon exiting the adhesive, then, the transducer can receive a reflected portion of the ultrasonic signal. Thereafter, the processing element can identify a defect, such as soft or improperly cured regions, in the adhesive upon a relationship of an amplitude of the reflected portion of the reflected ultrasonic signal to a predefined threshold.

Abstract: A method of analysis long range guided wave data reflected from defects and geometric features such as welds in a structure. The method involves acquiring two sets of data, and time shifting one set of data relative to the other. Data points that match in time after the shifting are considered to represent defects or geometric features in the structure. The result of the method is exclusion of false signal data and automation of data analysis.

Abstract: The invention relates to a method for non-destructive testing of materials, in which at least two differently guided waves (modes) are produced in the solid body, each at at least one specified angle, the measured reflection values are placed in relation to a reference echo in order to obtain a relative reflection value, and the relative reflection values of the individual modes are again placed in relation to one another, thereby enabling the size and type of the defects to be determined.

Abstract: An internal condition of a concrete structure is objectively evaluated irrespective of surrounding noise or the shape of a hammer, by placing a vibration sensor in direct contact with a measuring surface so as to directly convert a vibration generated on the measuring surface into a corresponding voltage without the intervention of a medium such as air thereby to quantify the vibration generated on the measuring surface concerned. A structure diagnosis apparatus of the present invention includes a vibration unit for generating an elastic wave in a measuring object of a concrete structure, a vibration detector adapted to be placed in contact with a surface of the measuring object for detecting a component in a predetermined frequency range of an elastic vibration generated on the surface of the measuring object by the vibration unit; and a display device for displaying a maximum amplitude of an output signal of the vibration detector.

Abstract: A method of ultrasound inspection is provided. The method includes providing a composite first part, introducing ultrasound to the part, receiving reflections of the ultrasound introduced in the first part, and predicting a residual strength of the first part using an amplitude of the received reflections.

Abstract: A system for inspecting adhesive in a composite structure, such as for soft or improperly cured regions, includes a transducer and a processing element. The transducer can transmit a signal, such as an ultrasonic signal, into the adhesive such that at least a portion of the ultrasonic signal can propagate through the adhesive, reflect off of an interface between the adhesive and another material, and propagate back through the adhesive. Upon exiting the adhesive, then, the transducer can receive a reflected portion of the ultrasonic signal. Thereafter, the processing element can identify a defect, such as soft or improperly cured regions, in the adhesive upon a relationship of an amplitude of the reflected portion of the reflected ultrasonic signal to a predefined threshold.

Abstract: A device for examining materials, in particular trees, other kinds of wood, and concrete, with a pulse generator (1) for generating a pulse that can be introduced into the material (2), with at least one sensor (3) adapted for being associated to the material (2) for detecting the pulse, and with an electronic evaluation device (4) for discriminating the pulse from interference pulses, is designed and constructed with respect to a universal application to even large test pieces of the material (2) being examined in such a manner that an electronic evaluation device (4) is associated to each sensor (3).

Abstract: The present invention uses the generation and detection of acoustic guided waves to evaluate the condition of the insulation on electrical wiring. Low order axisymmetric and flexural acoustic modes are generated in the insulated wire and travel partially in the center conductor and partially in the outer insulation. The stiffness of the insulation and the insulation's condition affect the overall wave speed and amplitude of the guided wave. Analysis of the received signal provides information about the age or useful life of the wire insulation. In accordance with the present invention, signal transmission occurs at one location on the electrical wire to be evaluated, and detection occurs at one or more locations along the electrical wire. Additional receivers can be used to improve measurement accuracy. Either the transmission transducer or one or more receiver transducers may be angled at other than 90 degrees to the wire.

Abstract: A method for non-destructive testing of a weld joint of a bolt welded onto a contact area on a planar sheet metal using the lift ignition method uses directed ultrasonic signals. During the welding operation a weld pool having a modified material structure is formed beneath the contact area in the sheet metal. Ultrasonic signals are transmitted into the sheet metal using a directed and obliquely transmitting ultrasonic transmitter positioned at a coupling-in point A. An ultrasonic receiver is positioned at a coupling-out point B and receives the ultrasonic signals transmitted through the sheet metal at the coupling-out point B, an acoustic path being formed between the coupling-in point A and the coupling-out point B.

Abstract: A nondestructive inspection method for composite structures, including thick core structures, is disclosed that imparts a vibration force into the structure and analyzes the response over a range of frequencies to find possible damaged areas. The composite structure is struck to induce vibration at a series of test points and the response of the composite structure as a function of acceleration at each test point is measured. The structural anomalies in the composite structure occur at structural stiffness irregularities near anomalies and are detected with a Gapped Smoothing Method operating on the data and plotting a structural irregularity index as a function of frequency and position.

Abstract: A system and technique for detecting the presence of foreign material is presented. An ultrasound transmitter interrogates the bulk material and an array of detectors receives the off angle ultrasound scattering response of the bulk material. The presence of foreign material is determined when the off angle scattering response exceeds a predetermined threshold. The technique is especially suitable for the detection of bone in meat.

Abstract: An ultrasound system determines the presence of a foreign object in a container of fluid by measuring echo signals from the outer surface of the container and the inner surface of the container. The amplitude of the echo signals are compared to determine the presence of an object in the container. The system also determines viscosity of the contained fluid by measuring a through-transmission time through the container and the fluid, measuring an outer echo transmission time of an outer echo signal from the outer surface of the container and an inner echo transmission time of an inner echo signal from the inner surface of the container, and determining a time difference between the outer echo transmission time and the inner surface transmission time.

Abstract: The testing results, etc. of surface flaws such as cracks formed in or just below a surface of a body to be detected are displayed using colors within different color regions in the color space when displaying, on the basis of a preset threshold value, the test signal ranging in magnitude from zero to the threshold value and the test signal falling in magnitude beyond the threshold value while changing the color and/or the depth of color little by little within each of the color regions according to the magnitude of the test signal. This enables small flaw signals, etc. to be displayed without exception, thereby preventing small flaws, etc. from being overlooked.

Abstract: A plurality of wires (33, 34; 35, 36) are disposed near the bottom (23-25) of blade root sockets (16-18) of a rotating disk 39 of a gas turbine engine by vapor deposition and etching, the wires including connections to excitation nodes (40, 42) and detection nodes (41, 43). A nearby stationary member of the engine mounts an oscillator amplifier (55) which drives a coil (57) that excites the circuitry, and a coil (62) drives an amplifier (65) and a processor (67) which provides an indication of whether or not one or more of the wires are broken by a crack.

Abstract: The invention relates to a test device for the ultrasonic testing of strand material, comprising a) a stationary container that defines a substantially cylindrical interior space that has a larger diameter than the strand material and that has a cylinder axis, and b) a device for producing a peripheral water jacket that is associated either with at least one nozzle for a water feed disposed substantially tangential to an inner surface of the interior space and leading to said interior space, and/or with a bucket wheel that rotates about the cylinder axis and that is provided with a drive unit, and c) at least one ultrasonic probe that is linked with the container and that has an active surface that is freely accessible from the cylindrical interior space.

Abstract: Process and apparatus for displaying, measuring the size of and counting individual inclusions in suspension in moving liquid metal using an ultrasound sensor including emission and reception devices. Using the emission device, a series of ultrasound beam pulses is emitted within the liquid metal, and echoes reflected by the inclusions are received using the reception device. The reflected echoes are successively acquired and processed, and displayed as images which are analyzed to count and measure the diameter of inclusions. The sensor is calibrated by selectively placing in a path defined by the beam pulses at least one control reflector having predetermined dimensions and a geometry stable over time, successively acquiring and processing reflected echoes from the control reflector, displaying the reflected echoes from the control reflector as images, and analyzing the control reflector echo images to determine a relationship between amplitude of the images and the control reflector dimensions.

Abstract: Ultrasonic testing techniques may involve the measurement of ultrasonic waves from the tested part. These waves may reflect from surfaces of various layers within the part. Further, these waves may reflect from faults, defects, voids, fractures, and others. As such, the measured ultrasonic wave is a complex mix of these reflections. One method for detecting flaws, defects, and others may be to express the signal in terms of a set of basis functions. These functions may be summed to produce the measured signal. Further, basis functions may be chosen such that a select set of the basis functions characterize the fault and/or defect. In one exemplary embodiment, the coefficients associated with the basis function may be non-zero when a defect is present. As such, a defect may be detected quickly and automatically.

Abstract: In a method and a device for the ultrasonic monitoring of overlapping welded joints between a first sheet (44) and a second sheet (46 pulses are irradiated at an angle of between 15 and 80° into the first sheet (44) by means of a first rotating probe head (28), which a) is arranged on a mount (20), b) has a tyre (80) rotating about the axle body (50), coupled to the ultrasound transmitter (58) and rolling along the first sheet (44), parallel to the overlapping welded joint (78). On ultrasound investigation of the overlapping welded joint (78) the impulses transmitted to the second sheet (46) are received by means of a second receiving rotating probe head (30), of similar construction to the first rotating probe head (28).

Abstract: All independent acoustical physical constants (elastic constants, piezoelectric constants, dielectric constants and density) of a material are predetermined as a function of its chemical composition, and the calibration line between the acoustic velocity for each of the substrate crystal plane, the propagation direction and the propagation mode, and other chemical and physical properties is numerically calculated with ease without making any experiments.

Abstract: A method for detecting an obstruction in a flow duct is provided. The method includes the steps of directing gas through at least one port of the flow duct, measuring a flow noise level of the gas directed through the at least one port, and comparing the noise level with a predetermined noise level. In the event that the flow noise level exceeds the predetermined noise level by at least a threshold amount, then the method includes the step of indicating the presence of an obstruction in the at least one port.

Abstract: The present invention provides a method, system, and an apparatus for detecting anomalies in a wooden member. The apparatus includes a first roller device comprising a first array of transducers, and a second roller device comprising a second array of transducers. A first transducer in the first array of transducers communicates with more than one transducer in the second array of transducers. The apparatus may be designed such that the wooden member may pass between the first roller device and the second roller device. In addition, the first array of transducers and the second array of transducers maintain an orientation perpendicular to the moving direction of the wooden member as the first roller device and the second roller device roll along the wooden member. Each of the transducers operate in an ultrasonic frequency range. Also, each transducer in the first array of transducers is acoustically isolated from each other transducer.

Abstract: A process for measuring the bond of a coating on a substrate. Ultrasound echoes through the substrate of a test piece are collected and their amplitudes are measured, their decay being a function of the bond of a coating deposited on the opposite face of the substrate. Preliminary tests on calibration test pieces give a correlation function so that it is unnecessary to carry out expensive and uncertain mechanical tests on the test pieces.

Abstract: A method is described for examining a solidifying and/or hardening material such as cement, concrete or the like, using ultrasound waves emitted by an ultrasound transmitter, which penetrate the solidifying and/or hardening material, are continuously measured and analyzed. During solidification and/or hardening of the material, the signal shapes of the ultrasound waves penetrating the material, are recorded. The change with time of the compression wave velocity and/or the relative energy of the ultrasound waves and/or the frequency spectra of the ultrasound waves is extracted from the ultrasound wave shapes during the entire course of solidification and/or hardening of the material. This change with time of the compression wave velocity and/or the relative energy of the ultrasound waves and/or the frequency spectra of the ultrasound waves is approximated through a compensating function, preferably the Boltzmann function.

Abstract: In the ultrasonic flaw detection method and apparatus, wideband longitudinal ultrasonic waves are irradiated from an ultrasonic wave generator probe onto a weld portion of a coarse grained material; from the waveforms of flaw detection echoes that are subsequently obtained, the highest frequency component that can be extracted using time frequency analysis is then extracted; subsequent ½ magnification frequency components are then extracted sequentially; waveforms of a necessary plurality of frequency bands from among each of the frequency bands that were extracted and have undergone waveform separation are then multiplied, and waveform peaks that are formed by the multiplication are detected as being defect portion echoes generated by defect portions in the coarse grained material weld portion; and, as a result, information on the defect portion is obtained from the detected defect portion echo.

Abstract: An acoustic sensing system to measure an interior characteristic of an object, for example, density, the presence of defects, or bond integrity (of a laminated object). The system includes a first set of acoustic transducers acting as transmitters for transmitting acoustic wave energy at a single frequency, which acoustic wave energy interacts with the object in a sensing region to provide transmitted, scattered, and reflected wave energy. A transmitter mounting mechanism allows the transmitters to be positioned in such a way that acoustic energy reflected from the object sets up a reverberation between the transmitter and the object. A second set of acoustic transducers acting as receivers of acoustic wave energy is positioned opposite the transmitters in such a way that acoustic waves passing through the object are coupled to the receivers.

Abstract: A method and system for determining meat quality in cattle is provided. In preferred embodiments the method comprises obtaining an ultrasound measurement of a cattle specimen between the 12th rib and 13th rib at weaning age. The ultrasound measurement is utilized to extrapolate a harvest quality parameter. Based on the harvest quality parameter, and preferably a yield grade, the specimen is categorized. Particularly preferred harvest quality parameters are ribeye area, fat thickness, intramuscular fat and ribeye shape. Methods for determining tenderness, stress and intramuscular fat are described and claimed.

Abstract: An invention to measure of objects of non-homogeneous ultrasonic impedance in the testing path is provided to detect the present of flaws in any part of the object. The invention utilized a reference signal to compare against the actual signal derived from ultrasonic testing of the object. Reference signals are determined based upon the known or calculated properties of the object's layers or previously obtained signals measured from the object.

Abstract: A nondestructive inspection apparatus includes a vibrating section 11 which is adapted to be placed in pressure contact with a surface of a measuring object 16 for generating an acoustic elastic wave W, a receiving section 12 for receiving a reflected wave, a pushing mechanism 13 for pushing the vibrating section and the receiving section against the measuring object, a pushing force measurement section 14 for detecting pushing forces Fa, Fb during vibration, a vibration control section 10 for driving the vibrating section, and a reception signal processing section 15 for determining the internal defect based on a reception signal R.

Abstract: A method of monitoring the condition of a thermal barrier coating on a turbine blade or vane during operation of the turbine is provided. The method includes providing a means for receiving acoustic output of the blade or vane during operation of the turbine and monitoring the acoustic output over time, to determine the condition of the thermal barrier coating on the blade or vane. The acoustic output arises from a force on the blade or vane, such as that due to impact of particles, a pulse of gas pressure or constant gas flow. An apparatus employing the above method for monitoring the condition of the thermal barrier coating during operation of the turbine, is also provided.

Abstract: The present invention describes a method for determining reactor continuity of a polymerization reactor by non-linear dynamics. Specifically, the invention relates to a method of analyzing system variables to indicate gas phase reactor continuity in real-time and controlling the reactor continuity to maintain operability.

Abstract: A smart skin structure has vibration energy managing and steering capabilities. The skin can be used to managing vibrations in the skin or shell of a system, subcomponent, device, or structure. The skin has sensors coupled to the skin to obtain a response to vibrations. Actuators integral with the skin can be selectively activated to apply forces to the skin to confine or redirect vibration energy to one or more predetermined skin regions. The forces applied by the actuators can be controlled to create confinement power flows. Further, the skin actuators can be controlled using spatial derivatives of the vibration forces. The structure can be used in, but is not limited to, watercraft, aircraft, space vehicles, automobiles, marine devices, industrial machinery, machine tools, home appliances, buildings, bridges, and offshore oil platforms.

Abstract: An invention to measure of objects of non-homogeneous ultrasonic impedance in the testing path is provided to detect the present of flaws in any part of the object. The invention utilized a reference signal to compare against the actual signal derived from ultrasonic testing of the object. Reference signals are determined based upon the known or calculated properties of the object's layers or previously obtained signals measured from the object.

Abstract: A cleaving tool provides pressurized gas to the edge of a substrate in combination with a sharpened edge to cleave the substrate at a selected interface. The edge of the tool is tapped against the perimeter of a substrate, such as a bonded substrate, and a burst of gas pressure is then applied at approximately the point of contact with the edge of the tool. The combination of mechanical force and gas pressure separates the substrate into two halves at a selected interface, such as a weakened layer in a donor wafer.

Abstract: An array of dual-element transducers for automated, ultrasonic inspection of a weld seam in austenitic material is configured through the use of a schematic representation of the weld seam. The weld is divided into zones, and separate transducers are selected to inspect each zone. A creep-wave transducer is used to inspect the uppermost zone, and an L-wave transducer is used to inspect a lower zone. The L-wave transducer is connect to a computer processor to serve “double-duty” : it is used with one set of gate and gain settings to process direct reflections of the emitted sound, and with another set of gate and gain settings to process indirect, mode-converted reflections of the sound. Gate settings are determined by measuring sound path distances from the schematic. Test plates are used to determine sensitivity settings, and to confirm adequate width of field for each transducer.

Abstract: A non-destructive method for characterizing a sputter target material comprises the steps of sequentially irradiating a test sample of the sputter target material with sonic energy at a plurality of positions on a surface of the sample; detecting echoes induced by the sonic energy; discriminating texture-related back-scattering noise from the echoes to obtain modified amplitude signals; comparing the modified amplitude signals with said at least one calibration value to detect flaw data points and no-flaw data points; counting the flaw data points to determine a flaw count; counting the total flaw data points and the no-flaw data points to determine a total number of data points and calculating a cleanliness factor.

Abstract: Ultrasound echoes (L5, L8, etc.) through the substrate (2) of a test piece (1) are collected and their amplitudes are measured, their decay being a function of the bond of a coating (2) deposited on the opposite face of the substrate (2); preliminary tests on calibration test pieces give a correlation function so that it is no longer necessary to carry out expensive and uncertain mechanical tests on the test pieces (1).

Abstract: A method and apparatus for ultrasonic flaw detection of line focus type suitable for detection of flaws in nonmetallic materials included in an object. Ultrasonic transmitter and receiver elements of line focus type are opposed at a distance (L) with an object under test placed between them, and a maximum ultrasonic echo is obtained at a distance Lp expressed by: Lp=0.75(FT+FR)−{(CS/CW)−1}t where FT (mm) is the focal length in the medium of the ultrasonic transmitter element of line focus type, FR (mm) is the focal length in the medium of the ultrasonic receiver element line focus type, CS (m/sec) is the speed of ultrasound in an object under test, CW (m/sec) is the speed of ultrasound in the medium, and t (mm) is the thickness of the object under test.

Abstract: Ultrasonic techniques are applied to the measurement of wooden members to detect splitting during sawing operations and thereby allow modification of a sawing technique or change in saw cut placement.

Abstract: An ultrasonic testing method uses surface waves to prevent false detection of primary cracks, to lower the level of structural noises from grain boundaries, and to improve the detectability in the ultrasonic testing by surface wave testing of hot rolling rolls. A surface wave probe 10 capable of transmitting and receiving a surface wave is provided with a piezoelectric element 10A, a resin wedge 10C disposed on the front surface of the piezoelectric element 10A and a damping block 10B disposed on the back surface. The surface wave probe 10 is driven to produce a short pulse having a pulse length being at most 2.5 times the wavelength of the surface wave to be produced. A coupling liquid medium is supplied to the probe 10 in accordance with the peripheral speed of the roll to be tested. Depending on the height of the reflected waves measured, the grinding allowance of the roll is determined, and the roll is ground according to the thus-determined grinding allowance.